I was recently attacked, multiple times, by someone not in the vanguard. How is this possible? My understanding was that rearguard members can only support, not attack. Am I incorrect in this?

Screenshots below. User 'Ouhz' attacked, and is not in the vanguard.



http://tinypic.com/r/2qu5iep/6



http://tinypic.com/r/2z8zwc9/6

RearGuards can assist or attack, they're pretty vital to battles.

Ahh. I was only in the rearguard for the first battle i participated in, and don't remember attacking being an option. Of the 12 battles i've been in since, i'd never seen it, or at least not noticed it. The help section makes no mention of this.

My observation of my own teammates use of the 'support' function is that it is pretty much useless. Is that correct?

There are various ways to build a reaguard. Vanguards usually only have 1 purpose, you deadly nukers on standby.

Rearguards can be built for
Assist Boosting
Attack Building
Hybrid Combo building.

Rearguard with powerful cards can boost a lot per 10 mp, but cannot affford hitting enemy too many times before knocking them out.

Weak rearguard can boost and attack to keep the combo going, but their boosts are weak due to using weak cards... but the cost to build attack combo is cheap as the cards are usually 4 MP.

Rearguards have a lot of concentration, vanguards can go afk until the last 10 minutes of battle after their rear has setup the field for the vanguards to shine.

Van and rear are both important, rear fights throughout the match, Van is the nukers that ensure victory and point domination.

both can attack, here is a little breakdown:

Vanguard:
- can only attack if alive
- gets a 20% decrease in MP cost for attacking
- possible a dmg boost (i have not been able to confirm this)

Rearguard:
- can attack even if your vanguard is dead
- full mp cost
- can assist vanguard (increase their attack/defense)

both add to the attack combo
only rearguard can do the assist combo

Is the strength of a rearguard boost/assist impacted by the strength of their immortals?

If you're talking about the Assist/Combo rate, no it isn't.
If you're talking about how much they hit for, yes it is.